Refrigerating method and refrigerating device with combinatoin of magnetic refrigeration and regenerative gas refrigeration

ABSTRACT

The present invention provides a refrigeration method combining magnetic refrigeration and gas-based regenerative refrigeration, the method comprises: replacing part of or all of regenerators ( 2 ) in a gas-based regenerative refrigerator with magnetic regenerators ( 2 ), wherein part of or all of fillers in the magnetic regenerators ( 2 ) are magnetic refrigeration materials to form magnetic regenerators ( 2 ) with the same operating temperature ranges as that of the corresponding regenerators in the gas-based regenerative refrigerator; disposing the magnetic regenerators ( 2 ) respectively in magnet assemblies ( 4 ) for generating controllable and periodically-changing field strength, and performing coupling control on working sequence of the gas-base regenerative regenerator and magnetic field changing sequence of the magnet assemblies to realize combination of magnetic refrigeration and gas-based regenerative refrigeration. And an apparatus combining magnetic refrigeration and gas-based regenerative refrigeration is also provided, which comprises: a pressure wave generator ( 1 ), m regenerators ( 2 ), m phase difference adjusting mechanism ( 3 ), j magnet assemblies ( 4 ) for generating controllable and changeable field strength and a coupling control system ( 5 ), wherein m is an integer between 1 and 5, and j&lt;=m.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigeration method and apparatus inthe field of refrigeration and cryogenic engineering, and especially toa refrigeration method and apparatus combining magnetic refrigerationand gas-based regenerative refrigeration. Namely, the present inventionrealizes efficient composite refrigeration of magnetic refrigeration andgas-based regenerative refrigeration by replacing part of or all of theconventional regenerator fillers in a gas-based regenerativerefrigerator with the magnetic refrigeration materials, disposing themagnetic regenerators formed in such way in a magnetic field withcontrollable and changeable field strength and performing effectivecoupling between the working sequence of the gas-based regenerativerefrigerator and the magnetic field changing sequence.

2. Description of the Related Art

In terms of basic principle, magnetic refrigeration and gas-basedregenerative refrigeration are two different refrigeration technologiesrespectively.

Magnetic refrigeration technology implements refrigeration based on thephysical phenomenon that heat is released by the magnetic material tothe outside during the magnetization and is absorbed by the magneticmaterial from the outside during demagnetization. The study on magneticrefrigeration dates back to about 120 years ago. In 1881, Warburg firstobserved the heating effect of the metal iron in an applied magneticfield. In 1895, P. Langeviz discovered the magnetocaloric effect. Twoscientists, Debye (in 1926) and Giaugue (in 1927), concluded thatrefrigeration can be realized by adiabatic demagnetization. After that,due to the significant progress on the magnetic refrigeration materials(magnetocaloric materials) of paramagnetic salts, the adiabaticdemagnetization refrigeration technology developed rapidly in theultra-low temperature range (˜10⁻⁶K) and low temperature range (below 15K) after 1933. The discovery of Gd magnetocaloric effect and firstrealization of room temperature magnetic refrigeration by Brown in 1976inspired people's interest in the room temperature magneticrefrigeration. Theoretically, magnetic refrigeration could be applied toany temperature range, but due to the limitation of magneticrefrigeration materials magnet technology and engineering technologies,the overall progress on the room temperature magnetic refrigeration isrelatively slow. With the proposing of Active Magnetic Regenerator (AMR)and the progresses on room temperature magnetic refrigeration materialsand systems by AMES national laboratory and Astronautics Corporation ofAmerica in the late 1990s, the magnetic refrigeration technology againattracts extensive attention.

Gas-based regenerative refrigeration is based on compression andexpansion of working fluid under oscillating flow conditions, and ismainly used to obtain small or medium scale refrigerating capacity atlow temperatures. Ever since Stirling cycle was put forward in 1816,after long-term development, the gas-based regenerative refrigerationhave been developed into various forms of refrigerator such as Stirlingrefrigerator, Vuilleumier (VM) refrigerator, Gifford-McMahon (G-M)refrigerator, Solvay refrigerator, pulse tube (ST) refrigerator andthermoacoustic refrigerator. Although these refrigerators vary in thespecific structure, all of them could be viewed as including three majorparts: a pressure wave generator, regenerator and phase differenceadjusting mechanism for adjusting phase difference between the pressurewave and mass flow rate (as shown FIG. 1). A combination of aregenerator and phase difference adjusting mechanism is usually calledas a stage of the refrigerator. The main difference among the aboverefrigerators lies in different forms of pressure wave generators anddifferent forms of phase difference adjusting mechanisms for adjustingphase difference between the pressure wave and mass flow rate. And thecommon ground of the above refrigerators consists in that they all useregenerators for absorbing heat in the hot-blow period and releasingheat in the reverse cold-blow period. The difference between theregenerator of the gas-based regenerative refrigerator and the aboveActive Magnetic Regenerator (AMR) of the magnetic refrigerator is thatthe materials of regenerators in the gas-based regenerative refrigeratoronly serve as heat transfer mediums without capability of refrigeration

The magnetic refrigeration generally is based on the following threetechnologies: the magnetic refrigeration materials, magnets and thethermal engineering system. Advances in the magnetic refrigerationmaterials have been impressive. However, due to limited heat transfercoefficient and relatively small magnetocaloric temperature change(especially with less strong magnets), the temperature differencebetween heat transfer fluid and materials imposes strong adverseinfluence on the practical thermodynamic efficiency of the magneticrefrigerator. For this reason, the practical thermodynamic efficiency ofthe magnetic refrigerator is still very low although the intrinsicthermodynamic efficiency of the magnetic refrigeration is very high. Inaddition, the magnetic refrigerator often requires a complicated drivingmechanism due to requirement of both high intensity changing magneticfield and heat transfer fluid with changing flow direction.

S. Jeong et al. in 1994 (Adv. Cryo. Engi. 39B) reported a magneticrefrigeration experimental system based on Stirling cycle. The conceptof combining magnetic refrigeration and Stirling cycle was mentioned inthe report. However, it is found after careful analysis of the reportthat the system is just an AMR magnetic refrigeration system based onStirling thermodynamic cycle without real combination of magneticrefrigeration and gas-based regenerative refrigeration, let alonementioning the use of permanent magnets of low energy consumption whichcan generate periodically-changing high intensity magnetic fieldconveniently.

G. F. Nellis et al. in 1998 (Adv. Cryo. Engi. 43) reported a magneticrefrigeration experimental system based on G-M cycle. The concept ofcombining magnetic refrigeration and G-M cycle was mentioned in thereport. However, it is found after careful analysis of the report thatthe system is just an AMR magnetic refrigeration system based on G-Mthermodynamic cycle, without real combination of magnetic refrigerationand gas-based regenerative refrigeration, let alone mentioning the useof permanent magnets of low energy consumption which can generateperiodically-changing high intensity magnetic field conveniently.

Robert Schauwecker et al. proposed “a hybrid heat pump/refrigerator withmagnetic cooling stage” (US 2007/0186560 A1). Although the “hybrid” of“gas refrigerator” and “magnetic refrigeration” is mentioned in thepatent, the “gas refrigerator” and “magnetic refrigeration” areindependent processes in the cycle and are only continuous in time.Actually, what the patent have achieved is only an “internal cascade” of“gas refrigerator” and “magnetic refrigeration”, instead of a realcombination of gas-based regenerative refrigeration and magneticrefrigeration. In addition, the patent mentions several methods forchanging magnetic field at the locations of magnetocaloric materials.Although the implementation methods are not described in detail, it canbe obtained from the analysis of the description that there are manytechnical difficulties in implementing the methods (either requiring acomplicated magnet and driving mechanism, or causing huge energyconsumption). Thus, the methods cannot meet practical requirements.

SUMMARY OF THE INVENTION

This present invention aims to provide a refrigeration method andapparatus combining magnetic refrigeration and gas-based regenerativerefrigeration. Namely, The present invention realizes efficientcombination of magnetic refrigeration and gas-based regenerativerefrigeration by replacing part of or all of the conventionalregenerator fillers in a gas-based regenerative refrigerator withappropriate magnetic refrigeration materials, disposing the magneticregenerators formed in such way in a magnetic field with controllableand changeable field strength and performing effective coupling betweenthe working sequence of the gas-based regenerative refrigerator andmagnetic field changing sequence.

The technical solutions of the present invention are as follows.

The present invention provides a refrigeration method combining magneticrefrigeration and gas-based regenerative refrigeration, which includes:replacing part of or all of regenerators in a gas-based regenerativerefrigerator with magnetic regenerators, wherein part of or all offillers in the magnetic regenerators are magnetic refrigerationmaterials to form magnetic regenerators with the same operatingtemperature ranges as that of the corresponding regenerators in thegas-based regenerative refrigerator; disposing the magnetic regeneratorsrespectively in magnet assemblies for generating controllable andperiodically-changing field strength, and performing coupling control onworking sequence of the gas-based regenerative refrigerator and magneticfield changing sequence of the magnet assemblies for generatingcontrollable and changeable field strength, to realize combination ofmagnetic refrigeration and gas-based regenerative refrigeration.

The present invention further provides a refrigeration apparatuscombining magnetic refrigeration and gas-based regenerativerefrigeration, which includes: a pressure wave generator 1, mregenerators, m phase difference adjusting mechanism, j magnetassemblies for generating controllable and changeable field strength anda coupling control system 5 for performing coupling control on workingsequence of a gas-based regenerative refrigerator and magnetic fieldchanging sequence,. wherein m is an integer between 1 and 5, and j<=m;part of or all of the m regenerators are magnetic regenerators; and partof or all of fillers in the magnetic regenerators are magneticrefrigeration materials; magnetic refrigeration temperature ranges ofthe magnetic refrigeration materials in the magnetic regenerators arethe same as the corresponding temperature ranges of locations of themagnetic regenerators in the gas-based regenerative refrigerator;

The above components are connected in the following manner: the pressurewave generator 1 is connected via a fluid flow pipe with one end of afirst stage gas-based regenerative refrigerator consisting of a firststage regenerator 2 ₁ and a first stage phase difference adjustingmechanism 3 ₁ for adjusting phase difference between pressure wave andmass flow rate; and the other end of the first stage gas-basedregenerative refrigerator is connected with one end of a lower stagegas-based regenerative refrigerator via a fluid flow pipe, and so onuntil the last stage; the magnetic regenerators are respectivelydisposed in the corresponding magnet assemblies for generatingcontrollable and periodically-changing field strength; and the couplingcontrol system 5 for performing coupling control on working sequence ofthe gas-based regenerative refrigerator and magnetic field changingsequence is respectively connected with the pressure wave generator,phase difference adjusting mechanism and magnet assemblies forgenerating controllable and changeable field strength via a signaltransmission cable and/or pipe and/or mechanical device;

input signals of the coupling control system 5 are characteristicparameters of the working sequence of the pressure wave generator 1and/or characteristic parameters of the working sequence of respectivephase difference adjusting mechanisms; and output signals of thecoupling control system 5 are signals for controlling the magnetassemblies for generating controllable and changeable field strength.

The gas-based regenerative refrigerator is a Stirling refrigerator,Vuilleumier (VM) refrigerator, Gifford-McMahon (G-M) refrigerator,Solvay (SV) refrigerator, pulse tube refrigerator or thermoacousticrefrigerator.

The magnet assemblies generate controllable and changeable fieldstrength based on superimposition of magnetic vectors through relativemovement of two permanent magnets.

The refrigeration apparatus is a combined composite refrigeration systemof magnetic refrigeration and gas-based regenerative refrigeration,which is formed by combining i identical refrigeration apparatusescombining magnetic refrigeration and gas-based regenerativerefrigeration according to working sequence phase angle differences θ;wherein the working sequence phase angle differences θ are identical andequal to 360°/i or different from each other.

Through analysis, it can be obtained that, if a high intensity magneticfield of low energy consumption can be obtained, efficient combinationof magnetic refrigeration and gas-based regenerative refrigeration canbe completely realized in theory by replacing conventional regeneratorfillers in a gas-based regenerative refrigerator with appropriatemagnetic refrigeration materials, disposing the magnetic regeneratorsformed in such way in a magnetic field with controllable and changeablefield strength and performing effective coupling between workingsequence of the gas-based regenerative refrigerator and magnetic fieldchanging sequence. From the perspective of thermodynamics, the abovecombination can completely blend the magnetic refrigeration andgas-based regenerative refrigeration in the whole cycle by the magneticregenerators, and it is difficult to distinguish the magneticrefrigeration process from the gas-based regenerative refrigerationprocess. This combination not only can solve the problem of lowefficiency of the pure magnetic refrigerator (the intrinsic efficiencyof the combination is higher than that of the two independentrefrigeration methods), but also can solve the problem of requiring acomplicated heat transfer fluid driving mechanism in the pure magneticrefrigerator by sharing the working fluid between the gas-basedregenerative refrigeration and magnetic refrigeration. In addition, dueto the progresses on permanent magnet technology providing changeablemagnetic fields, the high intensity magnetic field of low energyconsumption which can be conveniently and periodically changed is nolonger a technical bottleneck, which make it more feasible to implementthe combination of gas-based regenerative refrigeration and magneticrefrigeration technically.

For a single magnet, to realize the change of magnetic field strength,it is usually required to input energy when the magnetic field strengthis increased and release energy when the magnetic field strength isdecreased, although this process is reversible, it is difficult tocompletely store and release the energy of this process technically,however this problem can be solved in the following way: combiningmultiple identical refrigeration apparatuses combining magneticrefrigeration and gas-based regenerative refrigeration according tocertain working sequence phase angle difference to form a combinedcomposite refrigeration system of magnetic refrigeration and gas-basedregenerative refrigeration, in this way, energy storage/release betweendifferent magnet assembles for generating controllable and changeablefield strength can be realized through working sequence differences ofdifferent magnet assembles in energy storage/release processes, therebyfurther increasing the composite refrigeration efficiency of therefrigeration apparatus of the present invention.

The refrigeration apparatus and method combining magnetic refrigerationand gas-based regenerative refrigeration of the present invention havethe following advantages:

magnetic refrigeration and gas-based regenerative refrigeration are twodifferent refrigeration methods, although both have high intrinsicthermodynamic efficiency, there are corresponding technical problemswith both refrigeration methods. Especially, limited by thecharacteristics of the existing materials and requirement of thecomplicated heat transfer fluid driving mechanism, the actual efficiencyof the magnetic refrigeration is still low and the mechanism iscomplicated. Through the present invention, the following advantages areobtained:

1. the present invention can solve the problem of low actual efficiencyof the pure magnetic refrigerator, thereby improving the refrigerationefficiency significantly;

2. the present invention can solve the problem of requiring acomplicated heat transfer fluid driving mechanism in the pure magneticrefrigerator by sharing the working fluid between gas-based regenerativerefrigeration and magnetic refrigeration;

3. a novel refrigeration method with high intrinsic thermodynamicefficiency can be achieved by replacing the conventional regeneratorfillers with magnetic refrigeration materials, the intrinsic efficiencyof the novel refrigeration method is higher than that of the puremagnetic refrigeration method and the pure gas-based regenerativerefrigeration method without an obvious increase of complexity of thewhole system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the structure of an ordinarygas-based regenerative refrigerator;

FIG. 2 is a schematic diagram illustrating the structure of arefrigeration apparatus combining magnetic refrigeration and gas-basedregenerative refrigeration according to the present invention;

FIG. 3 is a schematic diagram illustrating the structure of a permanentmagnet assembly for generating controllable and changeable magneticfield strength;

FIG. 4 is a schematic diagram illustrating the structure of arefrigeration system combining magnetic refrigeration and 5-stagegas-based Stirling refrigeration;

FIG. 5 is a schematic diagram illustrating the structure of arefrigeration system combining magnetic refrigeration and 5-stagegas-based Stirling refrigeration;

FIG. 6 is a schematic diagram illustrating the structure of arefrigeration system combining magnetic refrigeration and single stagegas-based Stirling refrigeration;

FIG. 7 is a schematic diagram illustrating the structure of arefrigeration system combining magnetic refrigeration and 2-stagegas-based GM refrigeration.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be further illustrated in combination withaccompanying drawings and embodiments.

FIG. 1 a schematic diagram illustrating the structure of a m-stagegas-based regenerative refrigerator (wherein the regenerator are allordinary regenerators). The m-stage gas-based regenerative refrigeratorincludes a pressure wave generator 1, m regenerators and m phasedifference adjusting mechanisms; wherein m is an integer between 1 and5. The above components are connected in the following manner: thepressure wave generator 1 is connected via a fluid flow pipe with oneend of a first stage gas-based regenerative refrigerator consisting of afirst stage regenerator 2 ₁ and a first stage phase difference adjustingmechanism 3 ₁ for adjusting the phase difference between pressure waveand mass flow rate; and the other end of the first stage gas-basedregenerative refrigerator is connected with one end of a lower stagegas-based regenerative refrigerator via a fluid flow pipe, and so onuntil the last stage.

The gas-based regenerative refrigerator may be Stirling refrigerator, VMrefrigerator, G-M refrigerator, SV refrigerator, pulse tube refrigeratoror thermoacoustic refrigerator.

FIG. 2 shows the refrigeration apparatus combining magneticrefrigeration and gas-based regenerative refrigeration, which includes apressure wave generator 1, m regenerators, m phase difference adjustingmechanisms, j magnet assemblies for generating controllable andchangeable field strength and a coupling control system 5 for performingcoupling control on the working sequence of a gas-based regenerativerefrigerator and magnetic field changing sequence; wherein m is aninteger between 1 and 5, j<=m.

Part of or all of m regenerators are magnetic regenerators filled withmagnetic refrigeration materials. The magnetic refrigeration temperatureranges of the magnetic refrigeration materials in the magneticregenerators are the same as the corresponding temperature ranges oflocations of the magnetic regenerators in the gas-based regenerativerefrigerator.

The magnetic regenerators are respectively disposed in the magnetassemblies for generating controllable and periodically-changing fieldstrength, and the magnet assemblies generate controllable and changeablefield strength based on the superimposition of magnetic vectors throughrelative movement of two permanent magnets. The input signals of thecoupling control system 5 are characteristic parameters of the workingsequence of the pressure wave generator 1 and/or characteristicparameters of the working sequence of part/all of the phase differenceadjusting mechanisms 3, and the output signals of the coupling controlsystem 5 are signals for controlling the change of magnetic field of themagnet assemblies for generating controllable and changeable fieldstrength.

Embodiment 1: a refrigeration system combining magnetic refrigerationand 5-stage gas-based Stirling refrigeration with a refrigerationtemperature of 5K and an ambient temperature of 300K

For each regenerator, 10 magnetic refrigeration materials with Curietemperatures or equivalent Curie temperatures ranging from 300K to 5K(the interval between respective Curie temperatures or equivalent Curietemperatures is about 6K) are selected, and the permanent magnetassembly 4 for generating controllable and changeable magnetic fieldstrength is a permanent magnet assembly for generatingperiodically-changing magnetic field strength, which consists of twopermanent magnets arranged co-axially and rotating relatively (as shownin FIG. 3). The system combining magnetic refrigeration and gas-basedregenerative refrigeration, as shown in FIG. 4, includes a pressure wavegenerator (compression chamber) 1, five magnetic regenerators, fivephase difference adjusting mechanisms (displacers), five permanentmagnet assemblies for generating controllable and changeable fieldstrength, a sequence coupling controller 5, a warm end heat exchanger 6and a cold end heat exchanger 7. The above components are connected inthe following manner: the pressure wave generator 1 is connected via afluid flow pipe through the warm end heat exchanger 6 with one end of afirst stage gas-based regenerative refrigerator consisting of a firststage regenerator 2 ₁ and a first stage phase difference adjustingmechanism 3 ₁ for adjusting phase difference between the pressure waveand mass flow rate; and the other end of the first stage gas-basedregenerative refrigerator is connected with one end of a lower stagegas-based regenerative refrigerator via a fluid flow pipe, and so onuntil the last stage, the end of the last stage refrigerator is providedwith a cold-end heat exchanger 7 for outputting the cooling capacity;the magnetic regenerators formed by replacing conventional regeneratorfillers with the magnetic refrigerant are respectively disposed incorresponding magnet assemblies for generating controllable andperiodically-changing field strength; and the coupling controller 5 forperforming coupling control on working sequence of gas-basedregenerative refrigerator and magnetic field changing sequence is via asignal transmission cable connected with the pressure wave generator 1,phase difference adjusting mechanism 3 and magnet assemblies 4 forgenerating controllable and changeable field strength.

Each magnetic regenerator is formed by filling 10 magnetic refrigerationmaterials into the magnetic regenerator in a descending order accordingto the Curie temperatures or equivalent Curie temperatures of the 10magnetic materials, and has the same operating temperature range as thatof the corresponding regenerator in the gas-based regenerativerefrigerator; the input signals of the sequence coupling controller 5are the movement signals of the compression piston in the pressure wavegenerator (compression chamber) 1; the output signals of the sequencecoupling controller 5 are relative movement signals for controlling thechange of magnetic field of the permanent magnet assemblies forgenerating controllable and changeable field strength; and the flow ofthe working fluid in the composite refrigeration system is basically thesame as that of conventional 5-stage gas-based Stirling refrigeration.This embodiment realizes the combination of magnetic refrigeration and5-stage gas-based regenerative refrigeration by introducing the magneticregenerators, permanent magnet assemblies for generating controllableand changeable field strength and the sequence coupling controller 5;the composite refrigeration system formed in such way can at leastdouble the refrigeration capacity at 5K with nearly no increase onenergy consumption.

Embodiment 2: a refrigeration system combining magnetic refrigerationand 5-stage gas-based Stirling refrigeration with a refrigerationtemperature of 5K and an ambient temperature of 300K

6 magnetic refrigeration materials with Curie temperatures or equivalentCurie temperatures ranging from about 30K to about 5K (the intervalbetween respective Curie temperatures or equivalent Curie temperaturesis about 5K) are selected, and the magnet assembly 4 for generatingcontrollable and changeable field strength is a permanent magnetassembly for generating periodically-changing field strength, whichconsists of two permanent magnets arranged co-axially and rotatingrelatively, as shown in FIG. 3. The system combining magneticrefrigeration and 5-stage gas-based Stirling refrigeration includes apressure wave generator (compression chamber) 1, four conventionalregenerators and one magnetic regenerator 2 _(m), five phase differenceadjusting mechanisms (displacers), a permanent magnet assembly forgenerating controllable and changeable field strength, a sequencecoupling controller 5, a warm end heat exchanger 6 and a cold end heatexchanger 7. The above components are connected in the following manner:the pressure wave generator 1 is connected via a fluid flow pipe throughthe warm end heat exchanger 6 with one end of a first stage gas-basedregenerative refrigerator consisting of a first stage conventionalregenerator 2 ₁ and a first stage phase difference adjusting mechanism 3₁ for adjusting phase difference between the pressure wave and mass flowrate; and the other end of the first stage gas-based regenerativerefrigerator is connected with one end of a lower stage gas-basedregenerative refrigerator via a fluid flow pipe, and so on until thelast stage, the end of the last stage gas-based regenerativerefrigerator is provided with a cold-end heat exchanger 7 for outputtingthe cooling capacity; the magnetic regenerator 2 _(m) formed byreplacing the conventional last stage regenerator fillers with themagnetic refrigerant is disposed in the magnet assembly for generatingcontrollable and periodically-changing field strength; and the couplingcontrol system 5 for performing coupling control on working sequence ofgas-based regenerative refrigerator and magnetic field changing sequenceis via a signal transmission cable connected with the pressure wavegenerator 1, the phase difference adjusting mechanism and the magnetassembly for generating controllable and changeable field strength.

The magnetic regenerator 2 _(m) is formed by filling 6 magneticrefrigeration materials into the magnetic regenerator in a descendingorder according to the Curie temperatures or equivalent Curietemperatures of these magnetic refrigeration materials, and has the sameoperating temperature range as that of the corresponding regenerator inthe gas-based regenerative refrigerator; the input signals of thesequence coupling controller 5 are the movement signals of thecompression piston in the compression chamber or movement signals of thedisplacer; and the output signals of the sequence coupling controller 5are relative movement signals for controlling the change of magneticfield of the permanent magnet assembly; and the flow of the workingfluid in the composite refrigeration system is basically the same asthat of conventional 5-stage gas-based Stirling refrigeration. Thisembodiment realizes the combination of 1-stage magnetic refrigerationand 5-stage gas-based regenerative refrigeration by introducing amagnetic regenerators 2 _(n), in the last stage, the permanent magnetassembly for generating controllable and changeable field strength andthe sequence coupling controller 5; the composite refrigeration systemformed in such way can at least generate double refrigeration capacityat 5K with nearly no increase on energy consumption.

Embodiment 3: a refrigeration system combining magnetic refrigerationand single stage gas-based Stirling refrigeration with a refrigerationtemperature of 5° C. and an ambient temperature of 30° C.

The single material of LaFeSiH based system is used as the magneticrefrigeration material, and the magnet assembly is a permanent magnetassembly for generating periodically-changing field strength, whichconsists of two permanent magnets arranged co-axially and rotatingrelatively, as shown in FIG. 3. The system combining magneticrefrigeration and single stage gas-based Stirling refrigeration, asshown in FIG. 6, includes a pressure wave generator (compressionchamber) 1, a magnetic regenerator 2, a phase difference adjustingmechanism (expansion chamber) 3, a permanent magnet assembly forgenerating controllable and changeable field strength, a sequencecoupling controller 5, a warm end heat exchanger 6 and a cold end heatexchanger 7. The above components are connected in the following manner:the pressure wave generator 1 is connected via a fluid flow pipe throughthe warm end heat exchanger 6 with one end of a magnetic regenerator 2;and the other end of the magnetic regenerator 2 is connected via a fluidflow pipe through the cold-end heat exchanger 7 with the phasedifference adjusting mechanism 3, wherein the magnetic regenerator 2 andthe phase difference adjusting mechanism 3 constitute a refrigerator;the magnetic regenerator 2 is disposed in the magnet assembly 4 forgenerating controllable and periodically-changing field strength; andthe coupling control system 5 for performing coupling control on theworking sequence of the gas-based regenerative refrigerator and magneticfield changing sequence is through a mechanical device connected withthe pressure wave generator 1, the phase difference adjusting mechanism3 and the magnet assembly 4 for generating controllable and changeablefield strength.

The percentage of H in the LaFeSiH is changed to obtain 20 magneticrefrigeration materials with different Curie temperatures. The magneticregenerator 2 is formed by filling these magnetic refrigerationmaterials in a descending order according to the Curie temperatures ofthese magnetic materials, and the operating temperature range of themagnetic regenerator is the same as that of the correspondingregenerator in the gas-based regenerative refrigerator; the inputsignals of the sequence coupling controller 5 are the movement signalsof the pistons in the compression chamber and expansion chamber; theoutput signals of the sequence coupling controller 5 are relativemovement signals for controlling change of magnetic field of the magnetassembly, wherein the input and output are coupled respectively by asimple mechanical device; and the flow of the working fluid in thecomposite refrigeration system is basically the same as that of theconventional single stage gas-based Stirling refrigeration. Thisembodiment realizes the combination of magnetic refrigeration andgas-based regenerative refrigeration by introducing the magneticregenerator, permanent magnet assembly for generating controllable andchangeable field strength and the sequence coupling controller. Therefrigeration efficiency at 5° C. of the refrigeration system in thisembodiment could be at least 20% higher than that of the conventionalsingle stage gas-based Stirling refrigeration.

Embodiment 4: a refrigeration system combining magnetic refrigerationand 2-stage gas-based G-M refrigerator with a refrigeration temperatureof 4.2K and an ambient temperature of 300K

8 different magnetic refrigeration materials with Curie temperatures orequivalent Curie temperatures ranging from 40K to 3K (the intervalbetween respective Curie temperatures or equivalent Curie temperaturesis about 5K), and the magnet assembly is a permanent magnet assembly forgenerating periodically-changing field strength, which consists of twopermanent magnets arranged co-axially and rotating relatively, as shownin FIG. 3. The system combining magnetic refrigeration and 2-stagegas-based G-M refrigeration includes a pressure wave generator 1(consisting of a compressor unit, a heat rejector and a gas distributingvalve unit), a conventional regenerator 2 ₁ and a magnetic regenerator 2₂, a phase difference adjusting mechanism (i.e. displacer), a permanentmagnet assembly 4 for generating controllable and changeable fieldstrength, a sequence coupling controller 5, a first-stage cold end heatexchanger 7 ₁ and a second-stage cold end heat exchanger 7 ₂. The abovecomponents are connected in the following manner: the pressure wavegenerator 1 is connected via a fluid flow pipe with one end of a firststage gas-based regenerative refrigerator consisting of the conventionalregenerator 2 ₁ and a first stage phase difference adjusting mechanism 3₁ for adjusting phase difference between the pressure wave and mass flowrate; and the other end of the first stage gas-based regenerativerefrigerator (its connecting pipe is provided with the first-stage coldend heat exchanger 7 ₁) is connected via a fluid flow pipe with one endof a second stage refrigerator consisting of the magnetic regenerator 2₂ and a second stage phase difference adjusting mechanism 3 ₂ foradjusting phase difference between the pressure wave and mass flow rate;the connecting pipe of the other end of the second stage refrigerator isprovided with the second-stage cold end heat exchanger 7 ₂; the magneticregenerator 2 ₂ formed by replacing conventional regenerator fillerswith the magnetic refrigerant is disposed in the magnet assembly 4 forgenerating controllable and periodically-changing field strength; andthe coupling controller 5 for performing coupling control on the workingsequence of the gas-based regenerative refrigerator and magnetic fieldchanging sequence is via a signal transmission cable connected with thepressure wave generator 1, the phase difference adjusting mechanism andmagnet assembly 4 for generating controllable and changeable fieldstrength.

The magnetic regenerator 2 ₂ is formed by filling 8 magneticrefrigeration materials into the magnetic regenerator in a descendingorder according to the Curie temperatures or equivalent Curietemperatures of these magnetic refrigeration materials, and has the sameoperating temperature range as that of the corresponding regenerator inthe gas-based regenerative refrigerator; the input signals of thesequence coupling controller 5 are the movement signals of thedisplacer; and the output signals of the sequence coupling controller 5are relative movement signals for controlling the change of magneticfield of the permanent magnet assembly 4 for generating controllable andchangeable field strength; and the flow of the working fluid in thecomposite refrigeration system is basically the same as that ofconventional 2-stage gas-based G-M refrigeration. This embodimentrealizes the combination of magnetic refrigeration and gas-basedregenerative refrigeration by introducing the magnetic regenerator,permanent magnet assembly for generating controllable and changeablefield strength and the sequence coupling controller; and the compositerefrigeration system formed in such way can at least generate doublerefrigeration capacity at 4.2K with nearly no increase on energyconsumption.

The above gas-based regenerative refrigerator is described as a systemincluding three components (namely pressure wave generator, regeneratorand phase difference adjusting mechanism). Actually, the above gas-basedregenerative refrigerator can also be in the following forms:

1. the pressure wave generator may be in a variety of forms, such as 1)a valveless compressor including a cylinder, piston and drivingmechanism (such as Stirling type and Stirling-pulse tube type); 2) acompressor and a gas distributing valve(s) (such as G-M type, G-M-pulsetube type and SV type); 3) a thermal compressor (such as VM type andvarious types of thermoacoustic refrigerators);

2. the regenerator and the phase difference adjusting mechanism may beindependent of each other, or combined partially or completely; althoughthe above embodiments lists some magnetic refrigeration materials, itdoes not constitute any limitation to the available magneticrefrigeration materials of the present invention, the present inventiondoes not limit and it is unnecessary to limit the type and shape of themagnetic refrigeration material of the magnetic regenerator in any way.In fact, for a specific composite refrigeration system, many materialscan be selected as the magnetic refrigeration material. Those skilled inthe art will appreciate and admit that different structures andcombination forms of the practical refrigerators and the refrigeratorsof different materials shall be within the fundamental idea of thepresent invention, without limiting the spirit of the present inventionand scopes of the appended claims.

What is claimed is:
 1. A refrigeration method combining magneticrefrigeration and gas-based regenerative refrigeration, comprising:replacing part of or all of regenerators in a gas-based regenerativerefrigerator with magnetic regenerators, wherein part of or all offillers in the magnetic regenerators are magnetic refrigerationmaterials to form magnetic regenerators with the same operatingtemperature ranges as that of the corresponding regenerators in thegas-based regenerative refrigerator; disposing the magnetic regeneratorsrespectively in magnet assemblies for generating controllable andperiodically-changing field strength, and performing coupling control onworking sequence of the gas-based regenerative refrigerator and magneticfield changing sequence of the magnet assemblies for generatingcontrollable and changeable field strength, to realize combination ofmagnetic refrigeration and gas-based regenerative refrigeration.
 2. Arefrigeration apparatus combining magnetic refrigeration and gas-basedregenerative refrigeration comprising a pressure wave generator (1), mregenerators, m phase difference adjusting mechanism, j magnetassemblies for generating controllable and changeable field strength anda coupling control system (5) for performing coupling control on workingsequence of a gas-based regenerative refrigerator and magnetic fieldchanging sequence; wherein m is an integer between 1 and 5, and j<=m;part of or all of the m regenerators are magnetic regenerators; and partof or all of fillers in the magnetic regenerators are magneticrefrigeration materials; magnetic refrigeration temperature ranges ofthe magnetic refrigeration materials in the magnetic regenerators arethe same as the corresponding temperature ranges of locations of themagnetic regenerators in the gas-based regenerative refrigerator; andthe components are connected in the following manner: the pressure wavegenerator (1) is connected via a fluid flow pipe with one end of a firststage gas-based regenerative refrigerator consisting of a first stageregenerator (2 ₁) and a first stage phase difference adjusting mechanism(3 ₁) for adjusting phase difference between pressure wave and mass flowrate; and the other end of the first stage gas-based regenerativerefrigerator is connected with one end of a lower stage gas-basedregenerative refrigerator via a fluid flow pipe, and so on until thelast stage; the magnetic regenerators are respectively disposed in thecorresponding magnet assemblies for generating controllable andperiodically-changing field strength; and the coupling control system(5) for performing coupling control on working sequence of the gas-basedregenerative refrigerator and magnetic field changing sequence isrespectively connected with the pressure wave generator (1), phasedifference adjusting mechanism and magnet assemblies for generatingcontrollable and changeable field strength via a signal transmissioncable and/or pipe and/or mechanical device; input signals of thecoupling control system (5) are characteristic parameters of the workingsequence of the pressure wave generator (1) and/or characteristicparameters of the working sequence of respective phase differenceadjusting mechanisms; and output signals of the coupling control system(5) are signals for controlling the magnet assemblies for generatingcontrollable and changeable field strength.
 3. The refrigerationapparatus according to claim 2, wherein the gas-based regenerativerefrigerator is a Stirling refrigerator, Vuilleumier (VM) refrigerator,Gifford-McMahon (G-M) refrigerator, Solvay (SV) refrigerator, pulse tuberefrigerator or thermoacoustic refrigerator.
 4. The refrigerationapparatus according to claim 2, wherein the magnet assemblies generatecontrollable and changeable field strength based on superimposition ofmagnetic vectors through relative movement of two permanent magnets. 5.The refrigeration apparatus according to claim 2, wherein therefrigeration apparatus is a combined composite refrigeration system ofmagnetic refrigeration and gas-based regenerative refrigeration, whichis formed by combining i identical refrigeration apparatuses combiningmagnetic refrigeration and gas-based regenerative refrigerationaccording to working sequence phase angle differences θ; wherein theworking sequence phase angle differences θ are identical and equal to360°/i or different from each other.